Method for suppressing the evaporation of hydrogen fluoride from a mixing of hydrogen flouride and sulfone

ABSTRACT

A novel alkylation catalyst is described which is used in processes for alkylating olefin hydrocarbons with isoparaffin hydrocarbons to produce high octane alkylate products suitable for use as blending components of gasoline motor fuel. The novel catalyst comprises a mixture of a hydrogen halide, a sulfone and water and has suitable corrosion properties which permit its utilization in alkylation process systems. The novel alkylation catalyst is utilized in a novel process for alkylating olefin hydrocarbons with isoparaffin hydrocarbons. Also, described is a method for suppressing the rate of evaporation of hydrogen fluoride from a mixture of hydrogen fluoride and sulfolane that has been exposed to the atmosphere.

This is a continuation-in-part of application having Ser. No.07/877,336, filed May 1, 1992, now abandoned.

The present invention relates to a hydrocarbon conversion process and acatalyst composition to be utilized in said hydrocarbon conversionprocess. The invention further relates to a method of retardation orinhibition of corrosion in alkylation process systems by use of a novelcomposition. The invention also relates to the suppression of theevaporation of hydrogen fluoride from a solution upon its exposure tothe environment.

The use of catalytic alkylation processes to produce branchedhydrocarbons having properties that are suitable for use as gasolineblending components is well known in the art. Generally, the alkylationof olefins by saturated hydrocarbons, such as isoparaffins, isaccomplished by contacting the reactants with an acid catalyst to form areaction mixture, settling said mixture to separate the catalyst fromthe hydrocarbons, and further separating the hydrocarbons, for example,by fractionation, to recover the alkylation reaction product. Normally,the alkylation reaction product is referred to as "alkylate", and itpreferably contains hydrocarbons having seven to nine carbon atoms. Inorder to have the highest quality gasoline blending stock, it ispreferred that the hydrocarbons formed in the alkylation process behighly branched.

One of the more desirable alkylation catalysts is hydrofluoric acid,however, the use of hydrofluoric acid as an alkylation catalyst hascertain drawbacks. One of the primary problems with the use ofhydrofluoric acid as an alkylation catalyst is that it is a highlycorrosive substance, and it is toxic to human beings. The toxicity ofhydrofluoric acid to human beings is further complicated by the factthat anhydrous hydrogen fluoride acid is typically a gas at normalatmospheric conditions of one atmosphere of pressure and 70° F. It ispossible for the vapor pressure of hydrofluoric acid at standardatmospheric conditions to create certain safety concerns when it isexposed to the atmosphere. These safety concerns are created by the easewith which hydrofluoric acid is vaporized and released into theatmosphere.

In spite of the potential problems with human toxicity and the corrosivecharacteristics of hydrofluoric acid, industry has in the pastdetermined that the benefits from the use of hydrofluoric acid as analkylation catalyst outweigh the potential problems. For instance,hydrofluoric acid is an extremely effective alkylation catalyst in thatit permits the reaction of olefins by isoparaffins at low processpressures and process temperatures. HF is particularly suited for use asa catalyst in the alkylation of butylenes and, in the case of thealkylation of propylene and amylenes, HF has been used as an effectivecatalyst whereas other alkylation catalysts, such as sulfuric acid, havebeen found to be not as effective in such alkylation services.Additionally, the alkylate formed from a hydrofluoric acid alkylationprocess is of a very high quality having such desirable properties asbeing a mixture of highly branched hydrocarbon compounds that provide ahigh octane motor fuel. Generally, it has been found that the alkylateproduced by a hydrofluoric acid alkylation process has a higher octanevalue than that produced by typical sulfuric acid alkylation processes.Thus, it would be desirable to use an alkylation catalyst that has thedesirable features of the hydrofluoric acid catalyst but without havingits high vapor pressure.

In searching for a suitable composition to replace hydrofluoric acid asan alkylation catalyst having the desirable properties of providing fora high quality alkylate reaction product and a reduced vapor pressure,one problem encountered is that of the corrosive nature of suchsubstitute catalysts. Not only must such a substitute alkylationcatalyst have the aforementioned desirable physical properties, it mustalso be reasonably non-corrosive to the metal components, such as, forexample, pressure vessels, piping, equipment and other appurtenances, ofan alkylation process system in order for the catalyst to becommercially viable. In the case of the use of hydrogen fluoride as analkylation catalyst, the art teaches that, to minimize its corrosiveeffect upon the carbon steel components of this alkylation processsystem, it is best for the hydrogen fluoride to be used with a minimalconcentration of water. In fact, the corrosive effects of aqueoushydrogen fluoride on carbon steel increases with increasingconcentrations of water. As for the compositions proposed as beingsuitable substitutes for hydrogen fluoride as an alkylation catalyst,all have been found to also be highly corrosive to carbon steel.

It is, therefore, an object of this invention to provide a novelalkylation catalyst having the desirable property of providing a highquality alkylate reaction product when utilized in the alkylation ofolefins with paraffins but having a lower vapor pressure than that ofhydrofluoric acid.

A further object of this invention is to provide an alkylation catalystcomposition having suitable corrosion properties when utilized in analkylation process system such as one constructed of carbon steel.

A still further object of this invention is to provide a novelalkylation catalyst composition which can be used in an alkylationprocess system without causing commercially excessive corrosion of theprocess system's equipment.

A yet further object of this invention is to provide a process for thealkylation of olefins with paraffins in the presence of an alkylationcatalyst having the desirable property of having a reduced vaporpressure but which produces a high quality alkylate product.

Another object of this invention is to provide a method for inhibitingcorrosion of metal by a corrosive medium.

Yet another object of this invention is to provide a method forinhibiting or retarding the corrosive nature of compositions that cansuitably be used in processes and process systems for the alkylation ofolefins with paraffins.

Still, yet another object of this invention is to provide a method forsuppressing the evaporation of hydrogen fluoride from a mixturecontaining such hydrogen fluoride in the event that the mixture isreleased or exposed to the atmosphere.

Thus, the process of the present invention relates to the alkylation ofa hydrocarbon mixture comprising olefins and paraffins with a catalystcomposition comprising the components of a hydrogen halide, a sulfone,and water. Another embodiment of the present invention relates to amethod of inhibiting corrosion of metal by a corrosive medium comprisinga hydrogen halide and a sulfone by incorporating into said corrosivemedium water in an amount sufficient to inhibit corrosion.

The composition of the present invention comprises the components of ahydrogen halide, a sulfone, and water.

Another inventive method relates to the suppression of the evaporationof hydrogen fluoride from a mixture of hydrogen fluoride and sulfonewhen the mixture is exposed to the atmosphere. The method includes thestep of adding to the mixture of hydrogen fluoride and sulfone anevaporation suppressing amount of water to thereby suppress theevaporation of hydrogen fluoride from the mixture upon its exposure tothe atmosphere.

BRIEF DESCRIPTION OF DRAWINGS

Other objects and advantages of the invention will be apparent from theforegoing detailed description of the invention, the appended claims,and the drawings in which:

FIG. 1 is a bar diagram showing the corrosion rate of carbon steel inunits of mils of corrosion per year for various water concentration in ahydrogen fluoride and sulfolane mixture;

FIG. 2 is a bar diagram comparing the corrosion rate of carbon steel forvarious water concentrations in a hydrogen fluoride and sulfolanemixture in different test vessels; and

FIG. 3 is a schematic flow diagram of one embodiment of an alkylationprocess that utilizes the novel catalyst composition described herein.

FIG. 4 is a graphical diagram comparing the alkylate quality produced bythe alkylation of butenes by isobutane utilizing a catalyst compositioncomprising hydrogen fluoride and sulfolane with that produced with thecatalyst composition additionally containing water.

The novel composition of the present invention is suitable for use as analkylation catalyst and can comprise, consist of, or consist essentiallyof a hydrogen halide component, a sulfone component and water.

The hydrogen halide component of the catalyst composition or catalystmixture can be selected from the group of compounds consisting ofhydrogen fluoride (HF), hydrogen chloride (HCl), hydrogen bromide (HBr),and mixture of two or more thereof. The preferred hydrogen halidecomponent, however, is hydrogen fluoride, which can be utilized in thecatalyst composition in anhydrous form or in aqueous form; providedthat, the amount of water contained in the aqueous solution is not suchthat the ultimate water concentration in the alkylation catalyst orcomposition exceeds the desirable ranges described herein.

The sulfone component is an important and critical component of thecatalyst composition because of the several functions it serves andbecause of the unexpected physical properties that it imparts to thecatalyst composition. One important function of the presence of thesulfone component in the composition is its vapor pressure depressant orlowering effect upon the overall catalyst composition. It is anessential aspect of this invention for the sulfone component to besoluble in the hydrogen halide component and for the sulfone componentto be essentially immiscible with olefin and paraffin hydrocarbons so asto permit easy separation of the hydrocarbons from the catalystcomposition. Also, it is essential for the presence of the sulfonecomponent to have a minimal impact upon an alkylation reactionselectivity and activity.

Generally, those skilled in the art of hydrogen fluoride catalyzedolefin alkylation processing have known that to obtain the highestquality of alkylate from the aforementioned olefin alkylation process,it is essential for the hydrogen fluoride catalyst to be as free fromcontaminating compounds as is feasible. It is generally known that smallamounts of other compounds contained in the hydrogen fluoride catalystof an olefin alkylation process can have detrimental effects uponproduct alkylate quality by negatively affecting the selectivity of thealkylation reaction toward the production of a more desirableend-product; such as, for example, trimethylpentanes (TMP) in the caseof the alkylation of butylenes by isobutane. It is further known tothose skilled in the art that small amounts of components contained in ahydrogen fluoride alkylation catalyst can have a negative impact uponits activity toward the alkylation of olefins. Based upon the knowneffects of hydrogen fluoride catalyst contaminants upon the activity andselectivity of the alkylation process toward the production of highquality alkylate, one skilled in the art would expect that the additionof small to large amounts of a sulfone compound to a hydrogen fluoridecatalyst would have an enormously detrimental effect upon its catalyticperformance. However, it has been discovered that the presence of smallquantities of a sulfone compound in combination with hydrogen fluoridewill have little negative impact on the performance of the resultantmixture as an alkylation catalyst; but, it is further unexpected thatinstead of having a detrimental impact upon the catalytic performance, asmall concentration in an amount less than about 30 weight percent of asulfone component in combination with the hydrogen fluoride can enhancethe performance of the resultant composition as an alkylation processcatalyst.

Therefore, to take advantage of the vapor pressure depressant effects ofthe sulfone compound, it is desirable to utilize the sulfone in thecatalyst mixture in an amount wherein the weight ratio of the hydrogenhalide to the sulfone is in the range of from about 1:1 to about 40:1. Aweight ratio of hydrogen halide to sulfone in the catalyst mixture ofless than 1:1 has such a significantly negative impact upon alkylatequality when the composition is utilized as an alkylation reactioncatalyst that the composition becomes commercially ineffective as acatalyst. Thus, a 1:1 weight ratio of hydrogen halide to sulfone in thecatalyst mixture becomes a critical lower limit for this ratio. In thesituation where both vapor pressure depression and improved catalyticactivity and/or selectivity are desired, the composition that works bestin the alkylation of olefins will have a weight ratio of hydrogen halideto sulfone in the range of from about 1:1 to about 40:1. To achieveoptimal benefits from the catalyst composition, the preferred catalystmixture should have a weight ratio of hydrogen halide to sulfone in therange of from about 2.3:1 to about 19:1 and, more preferably, the weightratio shall range from 3:1 to 9:1.

The sulfones suitable for use in this invention are the sulfones of thegeneral formula

    R--SO.sub.2 --R'

wherein R and R' are monovalent hydrocarbon alkyl or aryl substituents,each containing from 1 to 8 carbon atoms. Examples of such substituentsinclude dimethylsulfone, di-n-propylsulfone, diphenylsulfone,ethylmethylsulfone, and the alicyclic sulfones wherein the SO₂ group isbonded to a hydrocarbon ring. In such a case, R and R' are formingtogether a branched or unbranched hydrocarbon divalent moiety preferablycontaining from 3 to 12 carbon atoms. Among the latter,tetramethylenesulfone or sulfolane, 3-methylsulfolane and2,4-dimethylsulfolane are more particularly suitable since they offerthe advantage of being liquid at process operating conditions of concernherein. These sulfones may also have substituents, particularly one ormore halogen atoms, such as for example, chloromethylethylsulfone. Thesesulfones may advantageously be used in the form of mixtures.

This novel alkylation catalyst composition solves many of the problemsthat herebefore have been encountered in typical alkylation processesthat use hydrofluoric acid as an alkylation catalyst. For instance, thisnovel catalyst composition has a significantly lower vapor pressure thanthat of the standard hydrofluoric acid alkylation catalyst. Theadvantage from using an alkylation catalyst having a much lower vaporpressure than that of hydrofluoric acid is that a lesser amount of theacid catalyst will vaporize and enter into the atmosphere in cases wherethe catalyst is exposed to the atmosphere. In particular, when making acomparison between the novel catalyst composition and hydrofluoric acid,one notices a significant difference in the vapor pressures of the twocatalysts. Since hydrofluoric acid has a substantial vapor pressure attypical atmospheric or ambient conditions, it is often in a vapor statewhen it is exposed to the atmosphere; thus, this vapor pressure makes itmore difficult to control and contain in cases where it is exposed tothe atmosphere.

The novel catalyst composition as described herein, solves many of theproblems associated with the use of hydrofluoric acid as a catalystsince it provides the benefit of having a lower vapor pressure atambient conditions than that of hydrofluoric acid. But, in addition tothe benefit of having a lower vapor pressure at ambient conditions, thenovel catalyst composition further can be utilized in typical alkylationprocesses to provide practical reaction rates at low operating pressuresand low operating temperatures to produce a high quality alkylateproduct which is suitable for use as a blending component of gasolinemotor fuel. A further benefit from the novel catalyst composition isthat it is easier to handle commercially than hydrofluoric acid.

In spite of the many advantages from the use of the novel compositioncomprising, consisting of, or consisting essentially of a hydrogenhalide component and a sulfone component, the compositions can have acorrosive effect upon metal when it comes into contact with such metal,for example, when the composition is utilized in an alkylation processsystem having carbon steel pressure vessels, piping, equipment and otherappurtenances. As earlier mentioned herein, those skilled in the art ofalkylation technology have known that small concentrations ofcontaminants contained in an alkylation catalyst can accelerate the rateat which corrosion occurs when the catalyst is contacted with a metalover that which would occur when the catalyst is free of a contaminant.One example of this phenomenon is in the case where anhydrous hydrogenfluoride is utilized as an alkylation catalyst. In this instance, it hasbeen known that aqueous hydrogen fluoride is a more corrosive mediumthan anhydrous hydrogen fluoride and that the greater the concentrationof water contained in the aqueous hydrogen fluoride, the more corrosiveis its nature when utilized in a carbon steel alkylation process system.An additional problem traditionally caused by the presence of water inthe catalyst system of an alkylation process is that it has a negativeimpact upon the ultimate alkylation end-product. Therefore, because ofthe aforementioned reasons, it is exceedingly unexpected for thepresence of water in an alkylation catalyst composition or system, ascontemplated by this invention, to have the effect of reducing orretarding the corrosive nature of the catalyst but without having asignificant impact on an alkylate end-product.

Thus, this invention contemplates the incorporation of water into acatalyst system or composition containing a hydrogen halide and asulfone in an amount sufficient to inhibit corrosion of a metal when thecatalyst system or composition comes into contact with the metal.Generally, it has been discovered that the concentration of the water inthe catalyst system can range from about 0.25 to about 10.0 weightpercent with the weight percent of the water being based on the sumweight of the hydrogen halide and sulfone components. The ranges of theweight ratio of the hydrogen halide component to the sulfone componentin the catalyst are those previously described herein. It is preferredfor the water to be present in the catalyst system in an amount in therange of from about 0.5 to about 10 weight percent and, most preferably,the water can be present in the range of from 1.0 to 5 weight percent.

It has also been discovered that, unexpectedly, water can be used tosuppress the evaporation of hydrogen fluoride from a mixture of hydrogenfluoride and sulfone when such a mixture is exposed to the atmosphere.As earlier described herein, combining a sulfone component with ahydrogen halide provides an effective alkylation catalyst mixture havinga reduced vapor pressure below that of the hydrogen halide itself. Ithas further been found that by adding to, or incorporating within, orutilizing with the mixture of hydrogen halide and sulfone, anevaporation suppressing amount of water the evaporation of the hydrogenhalide from the mixture will be suppressed upon its exposure to theatmosphere. Thus, a method for suppressing the evaporation of hydrogenfluoride from a mixture containing hydrogen fluoride and sulfone thathas been exposed to the atmosphere includes adding water to the mixturein an amount such that the rate of evaporation of the hydrogen halidefrom the mixture or solution is suppressed.

This method is useful primarily when a mixture of hydrogen halide andsulfone is released into the atmosphere from a volume defined by acontainment system. For the expected situation, the containment systemwill be an alkylation process system, but such a containment can be anysystem which defines a volume including, for example, storage vesselsand transportation vessels. In the situation where the mixture ofhydrogen halide and sulfone is released into the atmosphere from avolume defined by a containment system, the retention of the hydrogenhalide in the mixture or solution can be promoted by incorporating watertherein either before the release or after the release.

Generally, the hydrogen halide evaporation suppressing amount of waterto be added to, or incorporated within, or utilized with the mixture ofhydrogen halide, preferably hydrogen fluoride, and sulfone, preferablysulfolane, can be in the range of from about 0.001 weight percent toabout 10 weight percent based on the total weight of the mixture.Preferably, the hydrogen halide evaporation suppressing amount of wateradded to the mixture can be in the range of from about 0.1 to about 8weight percent and, most preferably, it can be in the range of from 1 to6 weight percent. The concentration ranges for the sulfone and hydrogenhalide in the mixture are described in detail elsewhere herein.

Alkylation processes contemplated by the present invention are thoseliquid phase processes wherein mono-olefin hydrocarbons such aspropylene, butylenes, pentylenes, hexylenes, heptylenes, octylenes andthe like are alkylated by isoparaffin hydrocarbons such as isobutane,isopentane, isohexane, isoheptane, isooctane and the like for productionof high octane alkylate hydrocarbons boiling in the gasoline range andwhich are suitable for use in gasoline motor fuel. Preferably, isobutaneis selected as the isoparaffin reactant and the olefin reactant isselected from propylene, butylenes, pentylenes and mixtures thereof forproduction of an alkylate hydrocarbon product comprising a major portionof highly branched, high octane value aliphatic hydrocarbons having atleast seven carbon atoms and less than ten carbon atoms.

In order to improve selectivity of the alkylation reaction toward theproduction of the desirable highly branched aliphatic hydrocarbonshaving seven or more carbon atoms, a substantial stoichiometric excessof isoparaffin hydrocarbon is desirable in the reaction zone. Molarratios of isoparaffin hydrocarbon to olefin hydrocarbon of from about2:1 to about 25:1 are contemplated in the present invention. Preferably,the molar ratio of isoparaffin-to-olefin will range from about 5 toabout 20; and, most preferably, it shall range from 8.5 to 15. It isemphasized, however, that the above recited ranges for the molar ratioof isoparaffin-to-olefin are those which have been found to becommercially practical operating ranges; but, generally, the greater theisoparaffin-to-olefin ratio in an alkylation reaction, the better theresultant alkylate quality.

Isoparaffin and olefin reactant hydrocarbons normally employed incommercial alkylation processes are derived from refinery processstreams and usually contain small amount of impurities such as normalbutane, propane, ethane and the like. Such impurities are undesirable inlarge concentrations as they dilute reactants in the reaction zone, thusdecreasing reactor capacity available for the desired reactants andinterfering with good contact of isoparaffin with olefin reactants.Additionally, in continuous alkylation processes wherein excessisoparaffin hydrocarbon is recovered from an alkylation reactioneffluent and recycled for contact with additional olefin hydrocarbon,such nonreactive normal paraffin impurities tend to accumulate in thealkylation system. Consequently, process charge streams and/or recyclestreams which contain substantial amounts of normal paraffin impuritiesare usually fractionated to remove such impurities and maintain theirconcentration at a low level, preferably less than about 5 volumepercent, in the alkylation process.

Alkylation reaction temperatures within the contemplation of the presentinvention are generally in the range of from about 0° F. to about 150°F. Lower temperatures favor alkylation reaction of isoparaffin witholefin over competing olefin side reactions such as polymerization.However, overall reaction rates decrease with decreasing temperatures.Temperatures within the given range, and preferably in the range fromabout 30° F. to about 130° F., provide good selectivity for alkylationof isoparaffin with olefin at commercially attractive reaction rages.Most preferably, however, the alkylation temperature should range from50° F. to 100° F.

Reaction pressures contemplated in the present invention may range frompressures sufficient to maintain reactants in the liquid phase to aboutfifteen (15) atmospheres of pressure. Reactant hydrocarbons may benormally gaseous at alkylation reaction temperatures, thus reactionpressures in the range of from about 40 pounds gauge pressure per squareinch (psig) to about 160 psig are preferred. With all reactants in theliquid phase, increased pressure has no significant effect upon thealkylation reaction.

Contact times for hydrocarbon reactants in an alkylation reaction zonein the presence of the alkylation catalyst of the present inventionshould generally be sufficient to provide essentially completeconversion of olefin reactant in the alkylation zone. Preferably, thecontact time is in the range from about 0.05 minute to about 60 minutes.In the alkylation process of the present invention, employingisoparaffin-to-olefin molar ratios in the range of about 2:1 to about25:1, wherein the alkylation reaction mixture comprises about 40-90volume percent catalyst phase and about 60-10 volume percent hydrocarbonphase, and wherein good contact of olefin with isoparaffin is maintainedin the reaction zone, essentially complete conversion of olefin can beobtained at olefin space velocities in the range of about 0.1 to about200 volumes olefin per hour per volume catalyst (v/v/hr.). Optimum spacevelocities will depend upon the type of isoparaffin and olefin reactantsutilized, the particular compositions of alkylation catalyst, and thealkylation reaction conditions. Consequently, the preferred contacttimes are sufficient for providing an olefin space velocity in the rangeof about 0.1 to about 200 (v/v/hr.) and allowing essentially completeconversion of olefin reactant in the alkylation zone.

The process may be carried out either as a batch or continuous type ofoperation, although it is preferred for economic reasons to carry outthe process continuously. It has been generally established that inalkylation processes, the more intimate the contact between thefeedstock and the catalyst the better the quality of alkylate productobtained. With this in mind, the present process, when operated as abatch operation, is characterized by the use of vigorous mechanicalstirring or shaking of the reactants and catalyst.

In continuous operations, in one embodiment, reactants may be maintainedat sufficient pressures and temperatures to maintain them substantiallyin the liquid phase and then continuously forced through dispersiondevices into the reaction zone. The dispersion devices can be jets,nozzles, porous thimbles and the like. The reactants are subsequentlymixed with the catalyst by conventional mixing means such as mechanicalagitators or turbulence of the flow system. After a sufficient time, theproduct can then be continuously separated from the catalyst andwithdrawn from the reaction system while the partially spent catalyst isrecycled to the reactor. If desired, a portion of the catalyst can becontinuously regenerated or reactivated by any suitable treatment andreturned to the alkylation reactor.

Now referring to FIG. 3, there is presented a schematic flow diagram ofa riser-reactor process system 10 that can be used in the alkylation ofolefins by isoparaffins. Pressure and kinetic energies are imparted to ahydrocarbon mixture, or hydrocarbon feed, comprising olefin andisoparaffin hydrocarbons, by pump 12 that is utilized to charge the feedvia conduit 14 to reactor vessel 16. Reactor vessel 16 defines analkylation reaction zone wherein the hydrocarbon feed is reacted bycontact with the novel catalysts as described herein. Upon enteringreactor vessel 16, the hydrocarbon feed is intimately mixed with thenovel catalyst by any suitable mixing means 18 for dispersing thehydrocarbon feed into the catalyst. Suitable mixing means 18 caninclude, but are not limited to jets, nozzles, porous thimbles and thelike. The catalyst is fed to reactor vessel 16 via conduit 20 and thehydrocarbon feed mixture is charged to reactor vessel 16 through mixingmeans 18 via conduit 22.

The resultant reactor effluent from reactor vessel 16 passes by way ofconduit 24 to settler vessel 26 which defines a separation zone andprovides means for separating the reactor effluent into a hydrocarbonphase and a catalyst phase. The catalyst is then taken from settlervessel 26 by way of conduit 28 to pump 30. Pump 30 provides means forimparting both kinetic energy and pressure energy to the catalyst phasetaken from settler vessel 26 and feeding, or recycling, it to mixingmeans 18 via conduit 20. The hydrocarbon phase is taken from settlervessel 26 by way of conduit 32 to scrubber vessel 34, which defines ascrubbing zone, or removal zone, and provides removal means for removingtrace quantities of acid catalyst contained within the hydrocarbon phaseto produce a scrubbed hydrocarbon phase. Any suitable removal means canbe used; however, one preferred method is to contact the hydrocarbonphase, containing a trace concentration of acid catalyst, with a bed ofalumina material contained within scrubber vessel 34.

The scrubbed hydrocarbon phase is passed by way of conduit 36 todebutanizer 38, which defines a separation zone and provides separationmeans for separating hydrocarbons having more than four carbon atoms andhydrocarbons having less than five carbon atoms. The hydrocarbons havingmore than four carbon atoms pass via conduit 40 to product storagevessel 42. The hydrocarbons having less than five carbon atoms pass byway of conduit 44 to downstream processing.

The following examples demonstrate the advantages of the presentinvention. These examples are by way of illustration only, and are notintended as limitations upon the invention as set out in the appendedclaims.

EXAMPLE I

This example describes the experimental method used to determine thecorrosivity of an HF and sulfolane mixture towards carbon steel and thecorrosivity of the mixture towards carbon steel when variousconcentration levels of water are used to thus demonstrate theeffectiveness of water as a corrosion inhibitor. Two different testprocedures were employed in determining the corrosion rates of carbonsteel coupons. The following described Procedure 1 was used for tests1-20, and procedure 2 was used for tests 21-23.

Procedure 1

A single carbon steel coupon of dimensions 1×0.25×0.07 inches weighing1.5-2.0 g was accurately weighed and measured. This coupon was thensuspended in either a double-ended, teflon-lined monel sample cylinderof 150 mL capacity or a stainless steel sample cylinder of 75 mlcapacity by using teflon string through a hole in the coupon. Theposition of the coupon was such that the coupon would remain submergedin the test solution when the cylinder was placed in an uprightposition.

The cylinder was evacuated, charged with the test solution and capped.Heat tape and insulation were wrapped around the cylinder and thecylinder was placed in an upright position on an orbital shaker set torotate at 60 rpm. Temperature was maintained at 115° F.

At the conclusion of the test, the cylinder was cooled to roomtemperature and emptied of its contents. The coupon was then carefullyremoved from the cylinder and rinsed gently with sodium bicarbonatesolution, water and acetone. After air drying, the coupon was dippedinto an uninhibited HCl solution for 20 seconds, removed, washed againand gently polished with fine steel wool. The coupon was then weighedand measured accurately. Corrosion was calculated in mils per year,whereby a "mil" is defined as 0.001 inch.

Procedure 2

This procedure is similar to that of procedure 1 with the exception thata 300 cc hastelloy C autoclave replaced the monel or stainless steelsample cylinder as the test vessel. One coupon identical to those usedabove was suspended in the autoclave by teflon string so as to eliminatethe possibility for metal-metal contact while ensuring the coupon wouldbe submerged completely in the test solution. After suspending thecoupon, the test solution was added.

Temperature was maintained by a constant temperature bath circulatingthrough internal autoclave heating coils; the test solution was stirredat a rate of 500 rpm throughout the trial.

Upon completion of the test, the test solution was drained and thecoupon was treated as in procedure 1.

EXAMPLE II

This example presents data obtained by the previously describedexperimental method of Example I. The data presented in Table Idemonstrate, unexpectedly, that the presence of water in an HF andsulfolane mixture has no detrimental effect on the corrosivity of themixture towards carbon steel and that, in fact, the presence of smallquantities of water in the mixture has an inhibitive effect upon itscorrosive nature. FIGS. 1 and 2 are bar diagrams which present some ofthe corrosion data obtained by the method of Example I. These diagramsclearly illustrate that the presence of water in the HF and sulfolanemixture has a corrosion inhibitory effect when the mixture is contactedwith metal.

                  TABLE I                                                         ______________________________________                                        HF/Sulfolane Carbon Steel Corrosion Testing Summary                                              Conditions    Corr.                                        Test Medium                  Time,   Rate                                     Test #                                                                              % HF    % Sulf.  % H.sub.2 O                                                                         Temp. °F.                                                                      Days  MPY                                ______________________________________                                         1    76.5    23.5     --    120     17    7.84                                2    71.4    27.1     1.5   115     15    3.06                                3    68.9    25.5     5.6   115     15    5.06                                4    61.6    38.4     --    115     15    17.8                                5    58.8    36.4     4.8   115     15    6.10                                6    63.2    36.8     --    115     17    192                                 7    59.8    38.3     1.9   115     17    1.63                                8    100.0   --       --    115     17    1.24                                9    96.9    --       3.1   115     17    0.97                               11    58.2    38.8     2.0    85     4     22.4                               12    61.2    38.8     0.25   85     4     120                                13    64.8    35.2     0.085  85     4     183                                14    59.8    40.1     0.100 115     7     27.9                               15    61.3    38.5     0.241 115     7     31.9                               16    61.6    37.9     0.488 115     7     29.6                               17    63.5    36.5     0.036 115     5     59.8                               18    59.8    40.1     0.12  115     6     50.5                               19    61.7    38.2     0.12  115     6     31.9                               20    62.3    37.6     0.037 115     5     9.25                               21    60.3    39.6     0.03  115     4     281                                22    55.3    42.5     2.2   115     5     1.97                               23    60.1    39.4     0.5   115     5     13.1                               ______________________________________                                    

EXAMPLE III

This example describes the method used to evaluate liquid catalystsmixtures comprising hydrogen fluoride, sulfolane and water as catalystsfor the alkylation of mono-olefins by isobutane. Data are presenteddemonstrating the unexpected improvement in alkylate quality from theaddition of small amounts of water to the hydrogen fluoride andsulfolane catalyst.

HF, sulfolane and water (60 wt. % HF, 38 wt. % sulfolane and 2 wt. %water) and HF and sulfolane (60 wt. % HF and 40 wt. % sulfolane)mixtures were evaluated for alkylation performance in the riser-reactorprocess system depicted in the schematic flow diagram of FIG. 3. In atypical reaction, the feed, a 10:1 isobutane:2-butenes feed, wascontacted with the catalyst via a spray nozzle of 0.01 inch diameterorifice at a feed rate of 300 mL/hour. Temperature was maintained at 90°F. by circulating coolant from a constant temperature bath through ajacket surrounding the reactor. Reactor contents were maintained in theliquid phase by keeping the pressure at 100 psig. The contents of thereactor flowed from the reactor into the settler where phase separationoccurred. Hydrocarbon was then collected and isolated for alkylatequality evaluation by gas chromatography; the acid phase recirculated tothe reactor by way of a gear pump at a rate of approximately 700-750mL/hour. Catalyst activity was observed to reach a maximum, followed bya slow decline throughout the reaction. No attempt was made toregenerate the catalyst or maintain catalyst activity in any of the runscited, although it is known that replacement of small amounts ofcatalyst and/or removal of acid soluble oil byproducts would besufficient to maintain catalyst life indefinitely.

The data presented in Tables II and III were obtained by using theexperimental method described in this Example III. The data show thatthe presence of water has no deleterious effect on alkylate quality withthe alkylate having a suitably higher octane number which reflects asuitably high concentration of branched octane compounds in thealkylate. Table II presents the data obtained for the HF, sulfolane andwater catalyst mixture and Table III presents data obtained for an HFand sulfolane catalyst mixture. FIG. 4 graphically presents some of thedata provided in Tables II and III relating to the weight percent oftrimethylpentanes contained in the alkylate product. The graphicallydepicted data clearly demonstrates the enhancement in alkylate qualitythat is obtainable from the addition of a small quantity of water to asulfolane and HF catalyst mixture.

                                      TABLE II                                    __________________________________________________________________________    Alkylate Overview: 60/38/2 HF/Sulf/H20 + Ideal Feeds                          Time, hrs                                                                            1.5 3   6   10  12  15  1.8 21  24                                     __________________________________________________________________________    C5-7   17.30                                                                             15.16                                                                             12.19                                                                             9.42                                                                              6.94                                                                              7.46                                                                              8.44                                                                              7.21                                                                              7.25                                   C8     49.56                                                                             54.84                                                                             61.84                                                                             69.48                                                                             74.73                                                                             75.99                                                                             78.64                                                                             71.30                                                                             72.66                                  C9+    28.90                                                                             26.44                                                                             21.18                                                                             14.98                                                                             13.00                                                                             6.96                                                                              9.20                                                                              6.26                                                                              6.91                                   TMP    38.67                                                                             43.42                                                                             49.86                                                                             57.48                                                                             62.32                                                                             64.44                                                                             64.57                                                                             60.76                                                                             61.70                                  DMH    10.89                                                                             11.42                                                                             11.99                                                                             12.00                                                                             12.41                                                                             11.56                                                                             14.06                                                                             10.22                                                                             10.63                                  THP/DMH                                                                              3.55                                                                              3.80                                                                              4.16                                                                              4.79                                                                              5.02                                                                              5.58                                                                              4.59                                                                              5.94                                                                              5.80                                   R + M/2*                                                                             89.9                                                                              90.4                                                                              91.4                                                                              92.5                                                                              93.0                                                                              93.9                                                                              92.6                                                                              93.9                                                                              93.1                                   R-F    0.00                                                                              0.00                                                                              0.00                                                                              0.00                                                                              0.00                                                                              0.00                                                                              0.00                                                                              0.00                                                                              0.00                                   % Convert                                                                            100.00                                                                            100.00                                                                            100.00                                                                            100.00                                                                            100.00                                                                            100.00                                                                            100.00                                                                            100.00                                                                            100.00                                 __________________________________________________________________________    Time, hrs                                                                            27  30  42  48  53  66  72  90  96                                     __________________________________________________________________________    C5-7   8.07                                                                              7.81                                                                              8.67                                                                              7.88                                                                              9.32                                                                              8.89                                                                              8.00                                                                              9.28                                                                              6.92                                   C8     74.93                                                                             75.83                                                                             75.36                                                                             77.04                                                                             71.68                                                                             72.48                                                                             76.03                                                                             68.38                                                                             78.07                                  C9+    6.01                                                                              8.29                                                                              8.27                                                                              8.96                                                                              8.47                                                                              10.87                                                                             11.03                                                                             12.00                                                                             12.99                                  TMP    63.20                                                                             63.67                                                                             63.05                                                                             64.03                                                                             59.98                                                                             59.98                                                                             63.21                                                                             55.94                                                                             64.53                                  DMH    11.74                                                                             12.16                                                                             12.31                                                                             13.01                                                                             11.70                                                                             12.51                                                                             12.82                                                                             12.44                                                                             13.54                                  TMP/DMH                                                                              5.38                                                                              5.24                                                                              5.12                                                                              4.92                                                                              5.13                                                                              4.80                                                                              4.93                                                                              4.50                                                                              4.77                                   R + M/2*                                                                             93.8                                                                              93.5                                                                              93.4                                                                              93.4                                                                              93.3                                                                              92.9                                                                              93.0                                                                              92.4                                                                              92.7                                   R-F    0.00                                                                              0.00                                                                              0.09                                                                              0.07                                                                              0.00                                                                              0.15                                                                              0.00                                                                              0.17                                                                              0.00                                   % Convert                                                                            100.00                                                                            100.00                                                                            100.00                                                                            100.00                                                                            100.00                                                                            100.00                                                                            100.00                                                                            100.00                                                                            100.00                                 __________________________________________________________________________     *Calculated                                                              

                                      TABLE III                                   __________________________________________________________________________    Total Product Stream Alkylates: 60/40 HF/Sulfolane + Ideal Feeds              Time, hrs                                                                            3   6   12  22  24  27  33  36  48                                     __________________________________________________________________________    C5-7   6.30                                                                              9.62                                                                              5.93                                                                              6.52                                                                              7.83                                                                              7.37                                                                              7.93                                                                              7.65                                                                              9.74                                   C8     59.57                                                                             54.39                                                                             74.58                                                                             69.73                                                                             67.55                                                                             62.14                                                                             65.07                                                                             67.35                                                                             60.44                                  C9+    14.03                                                                             4.24                                                                              9.90                                                                              12.42                                                                             13.05                                                                             14.87                                                                             11.02                                                                             14.19                                                                             9.91                                   TMP    50.32                                                                             47.25                                                                             60.38                                                                             58.26                                                                             56.38                                                                             51.95                                                                             54.27                                                                             56.06                                                                             50.45                                  DMH    9.25                                                                              7.14                                                                              14.20                                                                             11.47                                                                             11.16                                                                             10.18                                                                             10.81                                                                             11.29                                                                             9.99                                   TMP/DMH                                                                              5.44                                                                              6.62                                                                              4.25                                                                              5.08                                                                              5.05                                                                              5.10                                                                              5.02                                                                              4.96                                                                              5.05                                   R + M/2*                                                                             93.0                                                                              94.2                                                                              93.0                                                                              93.1                                                                              92.9                                                                              92.6                                                                              93.0                                                                              92.7                                                                              92.9                                   R-F    0.41                                                                              0.86                                                                              0.36                                                                              0.41                                                                              0.41                                                                              0.37                                                                              0.54                                                                              0.45                                                                              0.75                                   % Convert                                                                            100.00                                                                            100.00                                                                            100.00                                                                            100.00                                                                            100.00                                                                            100.00                                                                            100.00                                                                            100.00                                                                            100.00                                 __________________________________________________________________________    Time, hrs  51      54      57      73                                         __________________________________________________________________________    C5-7       8.25    7.86    7.19    7.10                                       C8         67.19   67.18   68.95   68.02                                      C9+        12.37   11.86   13.77   15.63                                      TMP        55.96   56.08   57.63   56.51                                      DMH        11.23   11.11   11.31   11.52                                      TMP/DMH    4.99    5.05    5.09    4.91                                       R + K/2*   92.8    93.0    92.8    92.5                                       R-F        0.55    0.51    0.38    0.50                                       % Convert  100.00  100.00  100.00  100.00                                     __________________________________________________________________________

EXAMPLE IV

This example describes the experimental method used to determine thevapor pressure of various hydrogen fluoride and sulfolane mixtures andto present vapor pressure data for such mixtures demonstrating theeffectiveness of sulfolane as a vapor pressure depressant.

A 100 mL monel bomb was dried and evacuated, followed by the addition ofa prescribed amount of anhydrous hydrogen fluoride. A specific amount ofsulfolane was then added to the bomb. Once the bomb achieved the desiredtemperature, the pressure within the bomb was recorded. The vaporpressure was assumed to be that of HF vapor alone (sulfolane has aboiling point of 283° C.). Table IV presents a portion of the vaporpressure data obtained by this experimental method and illustrates thechange in vapor pressure of the novel hydrogen fluoride and sulfolanecatalyst mixture as a function of the weight percent sulfolane in thecatalyst mixture.

                  TABLE IV                                                        ______________________________________                                        Vapor pressure of HF/sulfolane mixtures at 30° C.                      Wt. %        Vapor Pressure                                                   Sulfolane    (Torr)                                                           ______________________________________                                        0.00         1086                                                             3.82         1044                                                             4.75         1032                                                             7.36         1021                                                             7.65         1004                                                             13.01        972                                                              16.57        946                                                              19.90        897                                                              19.95        902                                                              24.11        862                                                              26.95        819                                                              29.01        794                                                              30.02        812                                                              36.70        680                                                              55.40        413                                                              71.96        187                                                              83.91         74                                                              ______________________________________                                    

EXAMPLE V

This example describes the method which utilizes batch reactions to testthe feasibility of using a hydrogen fluoride and sulfolane mixture as acatalyst for the alkylation of mono-olefins by isoparaffins. Data arepresented to demonstrate the unexpectedly improved properties of thealkylate product from such a catalytic process and to demonstrate thatfor certain concentration ranges the catalyst mixture unexpectedlyprovides a good quality alkylate.

HF/sulfolane mixtures were evaluated for alkylation performance in batchreactions at 90° F. In a typical trial, the desired amount of sulfolanewas added to a 300 mL monel autoclave under a blanket of nitrogen.Anhydrous HF was then introduced into the autoclave and heated to 90° F.with stirring at 500 RPM. The stirring was then increased to 2500 RPM,and an 8.5:1 isobutane:2-butenes mixture was added with nitrogenbackpressure at a rate of 100 mL/min. at a pressure of 150-200 psig.After 5 minutes, the stirring was stopped, followed by the transfer ofthe reactor contents to a Jerguson gauge for phase separation. Thehydrocarbon product was then characterized by gas chromatography.

The data presented in Table V were obtained by using the experimentalmethod described in this Example V.

                  TABLE V                                                         ______________________________________                                        Batch Results, Anhydrous HF/Sulfolane                                                Test Samples                                                                  No. 1 No. 2   No. 3   No. 4 No. 5 No. 6                                ______________________________________                                        mL sulfolane                                                                           0.00    13.00   28.00 38.00 50.00 50.00                              mL HF    100.00  93.50   86.00 81.00 75.00 50.00                              mL Feed  100.00  93.50   86.00 81.00 75.00 100.00                             wt. %    0.00    15.09   29.39 37.49 46.02 56.11                              sulfolane                                                                     % THP    65.40   71.28   67.29 57.14 52.21 20.45                              % DMH    9.63    9.02    10.52 1.1.90                                                                              12.28 1.58                               TMP:DMH  6.79    7.90    6.40  4.80  4.25  12.97                              C9+      5.81    10.56   10.98 16.49 18.96 0.28                               Organic  0.00    0.00    0.00  0.00  0.00  69.74                              fluorides                                                                     ______________________________________                                    

EXAMPLE VI

This example describes the steady state evaluation method for testingthe feasibility of using a hydrogen fluoride and sulfolane mixture as acatalyst for the alkylation of mono-olefins by isoparaffins. Data arepresented to demonstrate that for certain concentration ranges thecatalyst mixture unexpectedly provides a good quality alkylate.

A reactor was constructed to enable steady state evaluation ofHF/sulfolane alkylation catalysts using a 300 mL monel autoclave. A 10:1isobutane:2-butenes feed was introduced into the autoclave with stirringat 2000 RPM at a rate of 600 mL/hour. The reactor effluent flowed into amonel Jerguson gauge for phase separation. The hydrocarbon phase waspassed through alumina and collected, while the acid phase wasrecirculated to the reactor. Alkylate was evaluated by gaschromatography and by research and motor octane tests performed on testengines.

The data presented in Table VI was obtained by using the experimentalmethod described in this Example VI.

                  TABLE VI                                                        ______________________________________                                                     70/30    60/40    50/50  40/60                                          100%  HF/      HF/      HF/    HF/                                            HF    sulfolane                                                                              sulfolane                                                                              sulfolane                                                                            sulfolane                               ______________________________________                                        C8       93.5    81.1     82.2   56.9   26.95                                 TMP      86.3    70.5     70.4   46.1   22.26                                 DMH      7.1     10.6     11.7   10.6   4.54                                  TMP/DMH  12.1    6.6      6.0    4.4    4.90                                  C9+      3.4     3.9      8.1    23.1   36.32                                 R + M/2  97.0    95.5     94.9   93.7   NA                                    ______________________________________                                    

EXAMPLE VII

This example demonstrates the improvement in the retention of hydrogenfluoride in solution by the addition of water when a mixture of hydrogenfluoride and sulfolane is exposed to the atmosphere. The data show thatby adding small amounts of water to a mixture of hydrogen fluoride andsulfolane the hydrogen fluoride retention is enhanced over that where nowater is added.

Various mixtures of hydrogen fluoride and sulfolane, with and withoutwater, were placed into an 11"×11" open pan. The open pan was attachedto an electronic balance within a fume hood. The scale was connected toa computer which automatically took readings at 5-minute intervals. Thetemperature in each of the experimental runs was maintained at 68°±2° F.and the hood air velocity was maintained at 97 CFM. The data obtainedfrom these experiments are presented in Table VII. The data presented inTable VII show that the addition of a concentration of water to an HFand sulfolane mixture enhances the retention of HF in the mixture uponits exposure to atmospheric conditions.

                  TABLE VII                                                       ______________________________________                                        HF Retention in Various HF Solutions                                                   %               % HF Retained After                                  Mixture                                                                              % HF    Sulfolane                                                                              % H.sub.2 O.sup.a                                                                    10 Min                                                                              30 Min                                                                              60 Min                             ______________________________________                                        1      100      0       0      21    ˜0.sup.b                                                                       0                                 2      80      20       0      48    12     7                                 3      85      10       5      61    28     9                                 4      70      30       0      42    21    18                                 5      60      40       0      55    23    19                                 6      62      36       2      68    38    23                                 ______________________________________                                         .sup.a amount of added water                                                  .sup.b completely evaporated after 14 minutes                                 Temp = 68 ± 2° F. in all runs                                  

While this invention has been described in terms of the presentlypreferred embodiment, reasonable variations and modifications arepossible by those skilled in the art. Such variations and modificationsare within the scope of the described invention and the appended claims.

That which is claimed is:
 1. A method for suppressing the evaporation ofhydrogen fluoride from a mixture containing hydrogen fluoride andsulfone when said mixture is exposed to atmospheric conditionscomprising adding to said mixture a hydrogen fluoride evaporationsuppressing amount of water to thereby suppress the evaporation of HFfrom said mixture upon its exposure to the atmosphere.
 2. The method ofclaim 1 wherein said hydrogen fluoride evaporation suppressing amount ofwater is from about 0.001 to about 10 weight percent based on the totalweight of said mixture.
 3. The method of claim 2 wherein the weightratio of hydrogen fluoride to sulfone of said mixture is in the range offrom about 1:1 to about 40:1.
 4. The method of claim 3 wherein saidsulfone is sulfolane.
 5. A method for suppressing the evaporation ofhydrogen fluoride from a mixture containing hydrogen fluoride andsulfone, having been exposed to the atmosphere, comprising adding tosaid mixture a hydrogen fluoride evaporation suppressing amount ofwater.
 6. A method as recited in claim 5 wherein said hydrogen fluorideevaporation suppressing amount of water is from about 0.001 to about 10weight percent based on the total weight of said mixture.
 7. The methodas recited in claim 6 wherein the weight ratio of hydrogen fluoride tosulfone of said mixture is in the range of from about 1:1 to about 40:1.8. The method as recited in claim 7 wherein said sulfone is sulfolane.9. A method for retaining hydrogen fluoride in a mixture comprisinghydrogen fluoride and sulfone released into the atmosphere from a volumedefined by a containment system, comprising the step of incorporatingwater into said mixture in an amount sufficient to promote the retentionof hydrogen fluoride in said mixture upon its release into theatmosphere.
 10. A method as recited in claim 9 wherein said amount ofwater incorporated in said mixture is from about 0.001 to about 10weight percent based upon the total weight of said mixture.
 11. A methodas recited in claim 10 wherein said amount of water incorporated intosaid mixture is from about 0.1 to about 8 weight percent based upon thetotal weight of said mixture.
 12. A method as recited in claim 11wherein the weight ratio of hydrogen fluoride to sulfone of said mixtureis in the range of from about 1:1 to about 40:1.
 13. A method as recitedin claim 12 wherein the weight ratio of hydrogen fluoride to sulfone ofsaid mixture is in the range of from about 2.3:1 to about 19:1.
 14. Amethod as recited in claim 13 wherein sulfone is sulfolane.